---
title: "Short note: Factor of simultaneity Ks"
subject: "Industrial Power Distribution and Illumination"
chapter: 1
key: "semester_6/industrial_power_distribution_and_illumination:short-note-ks"
source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/short-note-ks
site: BCT Engineering
---

# Short note: Factor of simultaneity Ks

Industrial Power Distribution and Illumination · Chapter 1: Introduction

- Asked in: 2073 Bhadra, 2 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/short-note-ks
- Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-1

## Question

Write a short note on factor of simultaneity (Ks).

## Short answer

Factor of simultaneity (ks) = group maximum demand / sum of individual maximum demands (ks ≤ 1). Accounts for non-coincident peaks; reciprocal of diversity factor. Applied at each distribution level after ku. Typical values: 2-3 circuits 0.9, 4-5 0.8, 6-9 0.7, ≥10 0.6; lighting 1, sockets 0.1-0.2. Example: 5 motors each 7.5 kVA, ks=0.8 gives board demand 30 kVA.

## Answer

The **factor of simultaneity (ks)**, also called the coincidence factor, accounts for the fact that all loads of a group do not run at the same time. It is the ratio of the maximum demand of a group of loads to the sum of their individual maximum demands:

```text
ks = Max demand of group / Σ(individual MDs)
(ks ≤ 1)
```

It is the reciprocal of the diversity factor. ks is applied at each level of distribution (sub-board, main board, transformer) after ku has been applied to each load.

**Typical values (IEC 61439 for distribution boards):**

| Number of circuits | ks |
|---|---|
| 2 – 3 | 0.9 |
| 4 – 5 | 0.8 |
| 6 – 9 | 0.7 |
| 10 or more | 0.6 |

By function: lighting 1, heating and air conditioning 1, socket outlets 0.1–0.2.

**Example:** a board feeds 5 motors each with a demand of 7.5 kVA. With ks = 0.8, the board demand is 5 × 7.5 × 0.8 = 30 kVA instead of 37.5 kVA.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the factor of simultaneity?
   A. Rated power / actual power
   B. Average load / maximum demand
   C. Maximum demand / connected load
   D. Max demand of a group / sum of individual maximum demands
   Answer: D. ks accounts for the loads of a group not running at the same time. (Key point: Definition of ks)

2. How is ks related to the diversity factor?
   A. It is equal to the diversity factor
   B. It is the load factor
   C. It is the reciprocal of the diversity factor
   D. It has no relation
   Answer: C. ks = 1/diversity factor, so ks <= 1. (Key point: Relation to diversity)

3. A board feeds 5 motors of 7.5 kVA demand each with ks = 0.8. What is the board demand?
   A. 37.5 kVA
   B. 30 kVA
   C. 46.9 kVA
   D. 6 kVA
   Answer: B. 5 x 7.5 x 0.8 = 30 kVA. (Key point: Example)

## Related in Industrial Power Distribution and Illumination

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